Added reference pictures are pink
These are the things to check - 


naming/paths - try to put the images in a path without gaps, or non-standard characters. First try something like C:\test.jpg, where nothing should go wrong. 
path of your blender file, same as above.  
image format - open the images in an image editor, resave them
if these don't work, it might be some kind of a bug, specific to your operating system.